Human pituitary growth hormone. XX. Studies of the tryptophan residue

Brovetto-Cruz, Jorge; Li, Choh Hao

doi:10.1021/bi00840a006

Cited by 28 publications

(3 citation statements)

References 15 publications

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“…Only DNPS-ACTH was found to be less potent than the native hormone. Discussion o-Nitrophenylsulfenyl chloride has been widely used for the selective modification of tryptophan residues in a number of biologically active polypeptides and proteins (Scoffone et al, 1968; Brovetto-Cruz and Li, 1969;Ramachandran and Lee, 1970a;Ramachandran, 1970;Kawauchi et al, 1973). In the absence of sulfhydryl groups the reaction at acidic pH is highly specific for the indole group of the tryptophan residue.…”

Section: After Partitionmentioning

confidence: 99%

Chemical modification of the tryptophan residue in adrenocorticotropin

Canova-Davis¹,

Ramachandran²

1976

Biochemistry

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The single tryptophan residue in the pituitary hormone adrenocorticotropin was modified selectively by reaction with a variety of substituted o-nitrophenylsulfenyl chlorides. In addition to quantitative modification of the tryptophan residue, the reaction invariably resulted in partial oxidation of the methionine residue to the sulfoxide. The methionine sulfoxide derivative could be separated from the desired product by partition chromatography on Sephadex G-50 in the solvent system 1-butanol-pyridine-0.1% acetic acid (5:3:11). Thus, the 2,4-dinitrophenylsulfenyl, 2-nitro-4-carboxyphenylsulfenyl, and 2-nitro-4-carbamidophenylsulfenyl derivatives of adrenocorticotropin were prepared and characterized. Modifications in the isolation of adrenocorticotropin from ovine pituitaries are also described. The melanocyte stimulating activities of the native hormone and the analogues are discussed.

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Section: After Partitionmentioning

confidence: 99%

Chemical modification of the tryptophan residue in adrenocorticotropin

Canova-Davis¹,

Ramachandran²

1976

Biochemistry

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“…Whereas radioimmunoassays detect immunologic determinants which can vary with the specificity of the antiserum, radioreceptor assays appear to depend on ligand fields of more or less constant specificity (34)(35)(36)(37). hGH is thought (3,17,(34)(35)(36)(37)40) to possess at least two independent biological sites, one growth hormone-like and the other lactogenic.…”

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confidence: 99%

Structure‐function studies on human growth hormone

Aubert

Bewley

Grumbach

et al. 1986

International Journal of Peptide and Protein Research

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The relationship between the conformation of human pituitary growth hormone (hGH), biological activity, and ligand binding activity was studied by comparing conformational details previously published on in vivo and in vitro studies of identical samples of hGH and its known derivatives. In vivo assays included the rat tibia test for somatotropic activity and the pigeon crop‐sac assay for lactogenic hormone activity. Relative binding affinities were compared in radioimmuno‐assays using 125I‐hGH as tracer with 1) anti‐human chorionic somatomammotropin (hCS) serum (low discriminatory hybrid assay), 2) anti‐hGH sera (in conventional assays), 3) monospecific anti‐hGH serum (absence of cross‐reaction with hCS) and 4) human anti‐hGH sera obtained from GH‐deficient patients on replacement therapy. In addition, binding affinities were examined in two receptor‐binding assays, one specific for somatotropic activity (rabbit liver membranes, 125I‐hGH), and the other, for lactogenic hormones (rabbit mammary membranes, 125I‐oPRL). The conformational properties of native hGH and various chemically and enzymatically modified derivatives of the hormone were evaluated primarily from circular dichroism spectra, while conformational stabilities were estimated from the relative rates of tryptic digestion. Unfragmented, but chemically modified derivatives, exhibited good parallelism between retention or loss of native conformation and the in vivo potencies and in vitro binding affinities. None of the fragments of hGH showed activity in any of the radioreceptor assays or radioimmunoassays. Two derivatives of hGH, which contain gaps of 6 or 12 residues in the polypeptide backbone produced by partial enzymatic digestion, had full or increased in vivo potencies, full activities in the radioimmunoassays, and were the most active derivatives in both radio‐receptor assays. One of these, missing the hexapeptide corresponding to residues 135–140, was also found to retain nearly all the conformational properties of native hGH. These studies proved further evidence that 1) retention by modified forms of hGH of a high degree of in vivo biological potency or in vitro binding affinity is causally related to the retention of most of the conformation and conformational stability of the molecule, and 2) the biologically acitve, receptor‐binding and immunoreactive sites on the hGH molecule are 3‐dimensional in nature.

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“…The tryptophan residues of Iysozyme, trypsin, and chymotrypsin were fully modified by reacting the protein with 20 equivalents of a freshly prepared solutlon of 2-nitrophenylsulfenyl chloride in 50% acetic acid (354). Acetate buffer pH 4-5 has been used in the modification of human growth hormone (60), Iysozyme (341) and cx-lactalabumin (357).…”

Section: Cd~o~ ~Iomentioning

confidence: 99%